The present invention relates to a cell phone position measurement system and control method for measuring the position of a cell phone terminal by using the position measurement system.
Along with the spread of cell phone systems, more advanced services are being provided to cell phone terminals. One of the services is position information service which provides information corresponding to the position of a cell phone terminal by using a position measurement system from the cell phone terminal. Current position measurement methods are position measurement by GPS (Global Positioning System), position measurement based on the cell number of a cell phone system, and position measurement by the arrival time of the reception/transmission signal of the cell phone system.
GPS position measurement includes a single measurement method of measuring a position by a single terminal, a server-assist method of transmitting a message from a GPS satellite from a server connected to a network to a terminal and calculating a position by the terminal, and a server-driven method of transmitting, to a server on a network, a signal from a GPS satellite that has been received by a terminal and calculating the terminal position by the server.
FIG. 10 shows an example of coupling a cell phone system to a cell phone position measurement system using server-assist or server-driven GPS. In FIG. 10, the cell phone system comprises a plurality of cell phone terminals 3 and 27, and a cell phone network 2 connected to the cell phone terminals 3 and 27. The cell phone terminal 27 communicates voice and data with the cell phone terminal 3, and with a telephone set 5 and server 7 via a PSTN (Public Switched Telephone Network) 4 and Internet 6 connected to the cell phone network 2.
The GPS position measurement system is constituted by a plurality of GPS satellites 8a, 8b, and 8c which orbit around the Earth, a GPS reference receiver 9 which receives signals from the GPS satellites 8a, 8b, and 8c, a GPS terminal 28, and a GPS server 10 connected to the GPS reference receiver 9. The GPS reference receiver 9 is connected to the Internet 6. The GPS terminal 28 communicates with the cell phone terminal 27 by radio.
In the system obtained by coupling the cell phone system and position measurement system, the functions of these systems independently operate. By using position information such as a latitude and longitude measured by the position measurement system, the cell phone system utilizes the server 7 to provide services.
As shown in FIG. 11, the GPS terminal 28 comprises a GPS antenna 29 which receives a GPS signal, a GPS radio unit 30 which demodulates the received GPS signal, and a GPS decoder 31 which decodes the demodulated GPS signal. The cell phone terminal 27 has a transmission/reception antenna 32 which transmits/receives a radio signal to/from the cell phone system, a cell phone radio unit 33 which modulates/demodulates a transmitted/received radio signal, a system processor 34 which is connected to the cell phone radio unit 33 and processes a cell phone signal and GPS signal, a voice input/output unit 35, a voice processor 36, a display 37, a display processor 38, and a controller 39 which performs the overall processing.
FIG. 12 shows server-assist or server-driven GPS position measurement operation by the cell phone terminal 27 and GPS terminal 28. Steps S1 to S6 show sequence operations for performing channel connection between the GPS terminal 28, the cell phone terminal 27, and the cell phone network 2. In the cell phone terminal 27, the controller 39 issues a calling request to the call control layer of the system processor 34 (step S1). Upon reception of this calling request, the call control layer performs calling processing with respect to a radio channel control layer (step S2).
The radio channel control layer executes channel connection processing with respect to the radio channel control layer of the base station of the cell phone network 2 (step S3). The radio channel control layer sends a termination notification to the call control layer of the base station (step S5), and sends a channel connection response to the radio channel control layer of the cell phone terminal 27 (step S4). The call control layer of the cell phone terminal 27 receives a calling completion notification from the radio channel control layer (step S6). As a result, upper layer data is implemented from the controller 39 of the cell phone terminal 27 to the GPS server 10 (step S7).
To perform GPS position measurement in the channel-connected state, the controller 39 issues a GPS position measurement request to the GPS decoder 31 of the GPS terminal 28 via the system processor 34 (step S8). Upon reception of this request, a GPS block made up of the GPS antenna 29, GPS radio unit 30, and GPS decoder 31 receives signals from the GPS satellites 8a, 8b, and 8c and decodes them to perform GPS position measurement (step S9). After the end of GPS position measurement, the GPS decoder 31 notifies the controller 39 via the system processor 34 of the completion of position measurement (step S10). Then, the controller 39 executes, with respect to the GPS server 10, communication (transfer) associated with position information including transmission of a signal obtained by GPS position measurement (step S11).
In the conventional system, the radio unit 33 of the cell phone terminal 27 and the GPS radio unit 30 of the GPS terminal 28 operate independently. When the terminals 27 and 28 are located close to each other or the radio units 30 and 33 are housed in the same terminal, mutual interference occurs between the radio units 30 and 33. The GPS method exhibits a received radio field intensity much lower than the transmission power of a general radio system, and readily decreases the reception sensitivity by transmission radio waves. To prevent this, it is desirable to time-exclusively perform the operation of the GPS receiver and transmission signal processing operation.
However, a non-TDMA (Time Division Multiple Access) system such as an IMT-2000 (International Mobile Telecommunications 2000) system executes continuous transmission and does not have any transmission signal idle time. The GPS receiver cannot receive any signal in the transmission mode.
If the radio unit 33 of the cell phone terminal 27 stops transmission operation in order to avoid mutual interference between the radio units 30 and 32, the function layer which controls the call control function of the cell phone system undesirably performs channel recovery processing.